Ignition apparatus



March 14', 1939. E. B'. Nowosn-:LSKI

IGNIT ION APPARATU S Original Filed April 1'?, 1935 7 .M w e .No F 7 4 o5 fo 1 i B F .WQ Lr l 2 mi? E. .vll

IN V EN TOR.

Mm www jm 0 if Patented Mar. 14, 1939 PATENT OFFICE IGNITION APPARATUSEdward B. Nowosielski, Bloomfield, N. J., assignor to Eclipse AviationCorporation,

Orange, N. J., a corporation of New Jersey Original application April17, 1935, Serial No. 16,882. Divided and this application July 21, 1937,Serial N0. 154,845

12 Claims. (Cl. 123-169) This invention relates to spark plugs, and moreespecially to spark plugs for aviation engines. This application is adivision of my application No. 16,882, filed April 1'?, 1935.

The object oi this invention is to provide a spark plug, and moreespecially a shielded spark plug, the construction of which is such asto prolong its life and to insure its effectiveness in such service, andto4 aiord convenience, and which is economical to manufacture.

The invention comprises novel features of great utility in spark plugs,and novel combinations of elements making an improved spark plug and animproved assemblage of the spark plug and its high-tension conductor.

One phase of the invention involves a novel method oi' insuring againstdevelopment of "pipes along the edges of the rolled mica sheets employedas part of the insulating means.

In the accompanying drawing forming part hereof:

Fig. 1 is a view in elevation of one embodiment of the invention;

Fig. 2 is a longitudinal sectional view of the plug shown in Fig. 1 buton an enlarged scale;

Fig. 3 is a bottom plan view of certain of the inner elements of theplug as viewed along the plane indicated at 3 3 in Fig. 2;

Figs. 4 to 8 inclusive, indicate the appearance of the element 86 ofFigs. 1 and 2 as itpasses through the successive stages in the processof forming it into its ilnal condition. I

For the purpose of a shielded aviation spark plug the metal body I ofthe plug is provided with a shield extension II which extends upwardconsiderably above the upper end of the spindle I2 to enclose thespindle and the electrical connection between the same and the conductorwhich leads the high-tension current to the spindle. This shieldextension is preferably in one piece with the attaching nut 5, thoughsuch unity is not necessary.

Instead of completely closing the space between the shield extension IIand spindle I2, I provide a cooling and Ventilating chamber I3 in theform of an annular space between the shield extension II and a long thincylindrical metallic sleeve I4 having low thermal conductivity, andlined with a tube I5 formed of rolled mica constituting the wall of asecond chamber I6 bounded at its lower end by the upper surface of theco'mpressible metal .gland I1, and at its upper end by a novel heatdeiiecting and sealing assembly to be further described. The gland I l,instead of resting directly upon the lower mica stack I8, as

is the usual practice, is in contact with the upper end 2| of a sleeve22 provided for the purpose oi' absorbing the heat which nds its wayinto the mica stack I8 and deflecting said heat to the gland I1 andouter wail of the plug. Two other heat deflecting sleeves are shown at23, and 24, the former resting on the upper surface of the electrode cup25 secured in position on the base of the spindle I 2 by a pressuresufcient to change the cross-section of the upper end of the cup(initially of uniform bore) and causeits contour to conform to that ofthe, spindle base. 'Ihe part 24 is in the nature of a continuous jacketenclosing the spindle I2 and its insert 2'I of some metal (such ascopper or silver) having higher heatconductivity than thematerial-steel, preferably-used in the spindle proper. This sleeve orjacket 24 is shown as closed at its lower end but this closure occursonly after the jacket has been positioned upon the spindle, the jacketbeing initially, merely a thin tube open at either end. After beingplaced around the spindle the extending portion of the lower end is bentinwardly to lie ilat against the bottom surface of the spindle I2 andits insert 21-in other Words,

- to occupy the position indicated in Fig. 2. It will be noticed furtherthat the jacket 24 extends upwardly to a point just above the end of thegland I'I and the point where the centrally bored portion of the spindlebegins. Due to the reduction in cross-sectional area at this point, andalso by reason of the termination of the jacket 24 at this point, thereis a tendency to cut off much of the upward ilow of heat through thespindle I2 and to deilect the heat flow outwardly and radially into thecopper gland I'I from which much of the heat is directly dissipated bythe cooling blast circulating adjacent the central ilange'or shoulder 3|of the gland I'I, such circulation being produced by reason of theradial openings 32 and the annular chamber 33 communicating therewith.The sleeves 23 and 22 coact with the jacket 24 in diverting heatfrom'the spindle I2 and the electrode 25 to the annular chamber 34 andthe copper gland Il, and from said chamber and gland to the atmosphereby way of shell 36 and radial openings 32. In or adjacent the plane ofthese radial openings 32 there is provided a thrust washer 38 throughwhich pressure is applied to the gland II, and a compressible hoop orwasher 39 is provided to insure a iirm bond or seal preventing theescape of the confined cylinder gases, the pressure being applied as aresult of threading the shield extension II into the shell I0, the

ingly threaded as indicated at 4I.

As shown clearly in Fig. 2, the spindle I2 is of reduced diameter at twoor more points as indicated at 43 and 44; and the jacket 24, the rolledmica tube 46, and the soft metal gland I1 are pressed snugly into theseperipheral vdepressions in the spindle as one of the plug assemblingoperations. This operation of applying pressure laterally results notonly in a firm seal around the spindle I2 but also eliminates anylongitudinally extending crevices or "pipes which have heretofore been asource of leakage characteristic of rolled mica insulating tubes. Thewrapping of the mica sheets one around the other tends to leave suchcrevices running longitudinally of the wrapping, but by producing kinksat several points along the length of the wrapping, as indicated, I havefound it possible to eliminate this source of trouble.

As a means of maintaining the mica stack 48 in the compressed conditionand at the same time applying radial pressure to hold the mica lining I5of the inner metallic sleeve I4 in position, and at the same timeeffecting an additional path for the transfer of heat directly to thesaid sleeve I4 from which it may be radiated to the atmosphere by thecooling current of air flowing along the chamber I3 and the radialapertures 20 and 26, I propose to thread the upper end 5I of the spindleI2 and apply to said threaded portion 5I a pair of threaded collars ornuts 52 and 53, the latter having an external taper to receive acorrespondingly internally tapered collar 54 of softer material such ascopper so that it may, when subjected to the pressure applied by thetightening of nut 52, form a iirm bond with the washer 56 and also withthe expansion ring 58 which grips the mica lining I5 at a pointapproximately midway between its ends, this lining 58 being inserted andexpanded in the tube I4 prior to the assembly oi' said tube within theshield extension II. The associated elements 52, 53, 54 and 56, on theother hand, are first assembled separately in position upon the innerplug assembly, and the latter is then dropped in place Within the shell36 -prior to bringing the shield extension assembly into position. Alsoprior to attaching the upper assembly there is inserted within thehollowed portion of the spindle, a coil spring 6I and a contact pin 62having a circumferential shoulder 63 against which the upper end of thespring 6I abuts to urge said pin upwardly into position to contact theradially spread strands of the current conducting wire 66 when thelatter is installed in place. Associated with the wire 66 is itscovering 61 of insulatlng material, its outer metallic sheath 68, theflanged connection 69 soldered or otherwise secured thereto, and theattached coupling nut 1 I, all of which are brought into assembledrelationship with the parts previously described.

As noted above the inner end of the conductor 66 extends below theinsulating material 61 for a certain distance so that the strands may bespread apart to provide better contact with the end of the pin 62. Themethod of fastening the spread apart ends of the conductor is indicatedbest in Fig. 3 and includes the provision of a ilat metallic plate 13having a pair of notches 14 and 15 cut therein on opposite sides of thecentral aperture 16 through which the conductor 66 passes. Each of thespread apart sections of the stranded conductor is inserted intoposition within each of the slots 14 and 15 and thereupon the twoelements just mentioned being c'orrespond-- plate 13 pinched at eitherend to partially close the slots, the slot 15 being shown in thepartially closed position which it assumes after the pinching operation.The cable and plate 13 are then held in the assembled relation indicatedin Fig. 2 by the provision of a retainer or spacer sleeve 11 ofinsulating material such as porcelain glass or Bakelite, the upper endof the spacer 11 terminating in the plane of the lower surface of theflanged member 69. Also the upper outer surface of the spacer 11 is incontact with the inwardly and downwardly turned end of a ferrule 19 oflow thermal conductivity, the outer portion of which rests upon theshoulder 8i formed near the upper end of the heat dissipating inner wallI4 of the shield extension assembly.

As above indicated, one of the important features of the inventionconcerns the outer or grounded electrode and method of its manufactureand installation. The first step is to secure an H shaped metallic piece86 of suitable heat and spark resisting qualities while at the same timea sufficiently good conductor. Such a piece is indicated in Fig. 4. Thispiece is then subjected to a bending operation to bring it intosubstantially the form indicated in Fig. 5. Next the parallel sides 81and 88 are turned into semicircular arcs which preferably do not quitejoin (as indicated in Figs. 6 and 7) the cross-connecting portionremaining in the form to which it is initially bent, as shown in Fig. 5.The final step in formation of the electrode is to shape the upperannular surface formed by the semi-circular parts 81 and 88 so that intransverse section it will have the final appearance indicated in Fig.2. When thus completed the electrode receives a thin dished washer 9| ofsoft metal such as copper and then a second dished washer 92 of hardermaterial and preferably the same material as the electrode 86 itself.The installation and completion of the electrode assembly is thenobtained in the following manner: The shell 36 is placed on a table orWork-bench with its lower counterbore 94 uppermost, a thin cupshapedliner 95 of soft metal, preferably the same material as that oi.' thepiece 9i, and centrally apertured to a diameter corresponding to thediameter of the chamber 34, is then inserted in the recessed end 96. Theelectrode assembly consisting of the parts 86, 9| and 92 is then placedin position within the inverted cup member 95 and the assemblyconsisting of the parts 36, 91, 92, 9I and 86, is then placed in ahydrogen gas furnace or other suitable heat chamber and subjected to atemperature suflicient to cause a fusion or welding along the surfacesof the elements 91 and 9|, with the result that the five elements aboveenumerated become fused into a permanently welded single unit. This unitis then removed from the furnace, the core assembly, the shieldextension assembly, and upper cable assemblies successively attachedthereto in the respective manners above indicated. When this completeassembly has been accomplished it will be found that the inner electrode25 occupies a position approaching that of the transverse portion 86 ofthe outer electrode andalso approaching that of the inner cylindricaledge 99 of the thimble 92, forming an auxiliary spark gap, theclearances therebetween being such that the spark will normally jumpfrom the relatively broad surface of the electrode 25 to thecorrespondingly broad plane surface of the cross-piece 86 of the groundelectrode; but if for any reason this normal path of the spark isobstructed--as for example by the formation oi ice particlesthe -sparkcan then jump from the cylindrical surface of the electrode 25 to theabove described cylindrical surface 99 of the thimble 92 which 1. -.aytherefore be considered as a part of the compieted electrode. In fact,it is, of course, possible to have the elements 92, 9| and 86 originallyformed as an integral whole rather than being composed oi threesubsequently united pieces as shown.`

It will be noted that the mica tube 46 terminates somewhat above thelower flange oi' the heat conducting sleeve 23 oi copper or other metal,and that therefore a plurality of the mica disks i8 lie between the endof the mica tube and the said flanged portion of thel sleeve. Thisarrangement has the advantage of facilitating' maximum heat transferfrom the mica assembly I8 and deilecting such heat to the jacket 24 aswell as to the sleeve 22, and at the same time provides a better degreeof protection for the lower ends oi.' the layers constituting thecompleted tube 49. It will also be observed that the cylindrical portionof the sleeve 2l is externally tapered to facilitate a snugI grip andseal between parts 46, 23 and 24.

What is claimed is:

1. In a spark plug having a central spindle surrounded by a stack ofinsulating discs, and an enclosing shell, the combination with saiddiscs, spindle vand shell of metallic means including a pressure glandand a ilanged sleeve extending through apertures in said discs forfacilitating rapid transfer of heat from said discs to said shell theflanged part of said sleeve being in contact with said pressure gland.

2. In a spark plug having a central spindle surrounded by a stack ofinsulating discs, and an enclosing shell, the combination with saiddiscs, spindle and shell of metallic means including a pressure glandand a anged sleeve extending through apertures in said discs forfacilitating rapid transfer oi' heat from said discs to said shell theflanged part of said sleeve being in contact with said pressure gland,and a compressible hoop or washer thermally co-operating with saidpressure gland, and also with said shell.

3. A spark plug comprising a shell, an electrode supported in the shell,a tube of insulation disposed around the electrode, a soft metallicsealing bushing of high heatconductivity disposed centrally of theelectrode and in intimate thermal contact with the insulation, saidbushing having formed thereon a flange in contact with the shell,additional insulating material around the electrode above and below thebushing,` and a retaining means insertable between the bushing and shellto hold the parts in the shell.

4. A spark plug comprising a shell, an electrode supported in the shell,a tube of insulation dis` posed around the electrode, a soft metallicsealing bushing of high heat conductivity disposed centrally of theelectrode and in intimate thermal contact with the insulation, saidbushing having contact with the shell, additional insulating materialaround the electrode above and below the bushing, and a retaining meansinsertable between the bushing and shell to hold the parts in the shell,said retaining means being formed to receive a radio shielding means.

5. A spark plug comprising a shell, an electrode supported in the shell,a tube of insulation disposed around the electrode, a soft metallicsealing bushing of high heat conductivity disposed centrally of theelectrode and in intimate thermal contact with the insulation, saidbushing having formed thereon a ilange in contact with the shell. and aretaining means insertable between the bushing and shell to hold theparts in the shell, said electrode being formed with a bore extendingall the way down to the bushing to reduce the cross-sectional area oi.'the electrode abovethe bushing.

6. A spark plug comprising a shell, an electrode supported in the shell,a tube of insulation disposed around the electrode, a soft metallicsealing bushing of high heat conductivity disposed centrally of theelectrode and in intimate thermal contact with the insulation, saidbushing having formed thereony a ange in contact with the shell, and aretaining means insertable between the bushing and shell to hold theparts in the shell.

7. A spark plug comprising a shell, an electrode supported in the shell,a tube of insulation disposed around the electrode, a soit metallicsealing bushing of high heat conductivity disposed centrally of theelectrode and in intimate thermal contact with the insulation, saidbushing having formed thereon a flange iltting within the shell, and aretaining means insertable between the bushing and shell to hold theparts in the shell.

8. A spark plug comprising a shell, an electrode supported in the shell,a tube of insulation disposed around the electrode, a soft metallicseall ing bushing of high heat conductivity disposed centrally of the'electrode and in intimate thermal contact with the insulation, saidbushing having formed thereon a ilange fitting within the shell,additional insulating material around the electrode above and below thebushing, and a retaining means insertable between the bushing and shellto hold the parts in the shell, said retaining means being formed toreceive a radio shielding means.

9. A spark plug comprising a shell, an electrode supported in the shell,a tube of insulation disposed around the electrode, a soft metallicsealing bushing of high heat conductivity disposed centrally of theelectrode, a sealing bushing disposed centrally of the electrode and inintimate thermal contact with the insulation, said bushing having formedthereon a flange in contact with the shell, additional insulatingmaterial around the electrode above and below the bushing, and aretaining means insertable `between the bushing and shell to hold theparts in the shell.

10. A spark plug comprising a shell, an electrode supported in theshell, a tube of insulation disposed around the electrode, a softmetallic sealing bushing of high heat conductivity disposed centrally ofthe electrode and in intimate thermal contactv with the insulation, saidbushing having formed thereon a flange in contact with the shell,ladditional insulating material around the electrode above and below thebushing.. and a retaining means to hold the parts in the shell, saidretaining means including a member which, when screwed into the shell,applies pressure said shell contacting ange.

11. A spark plug comprising a shell. an electrode supported in theshell, 'a tube of insulation disposed around the electrode, a softmetallic sealing bushing of high heat conductivity disposed centrally oithe electrode and in intimate thermal contact with the insulation, saidbushing taining means to hold the parte in the shell. said retainingmeans including a member which, when screwed into the shell, appliespressure to :said sealing bushing.

12. A spark plug comprising a shell, an elec trode supported in theshell, a. tube 0I insulation disposed around the electrode, a softmetallic sealing bushing of high heat conductivity disposed centrally ofthe electrode and in intimate thermal contact with the insulation, saidbushing having Contact with the shell, additional in sulating materialaround the electrode above and below the bushing, and a retaining meansinsertable between the bushing and shell to hold the parts in the shell.

EDWARD B. NOWOSIEISKI,

